package org.protobee.util;

public class Base32 {
  private static final String base32Chars =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
  private static final int[] base32Lookup =
  { 0xFF,0xFF,0x1A,0x1B,0x1C,0x1D,0x1E,0x1F, // '0', '1', '2', '3', '4', '5', '6', '7'
    0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF,0xFF, // '8', '9', ':', ';', '<', '=', '>', '?'
    0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '@', 'A', 'B', 'C', 'D', 'E', 'F', 'G'
    0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O'
    0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W'
    0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF, // 'X', 'Y', 'Z', '[', '\', ']', '^', '_'
    0xFF,0x00,0x01,0x02,0x03,0x04,0x05,0x06, // '`', 'a', 'b', 'c', 'd', 'e', 'f', 'g'
    0x07,0x08,0x09,0x0A,0x0B,0x0C,0x0D,0x0E, // 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o'
    0x0F,0x10,0x11,0x12,0x13,0x14,0x15,0x16, // 'p', 'q', 'r', 's', 't', 'u', 'v', 'w'
    0x17,0x18,0x19,0xFF,0xFF,0xFF,0xFF,0xFF  // 'x', 'y', 'z', '{', '|', '}', '~', 'DEL'
  };

   static public String encode(final byte[] bytes)
  {
      int i =0, index = 0, digit = 0;
      int currByte, nextByte;

      // begin fix
      // added by jonelo@jonelo.de, Feb 13, 2005
      // according to RFC 3548, the encoding must also contain paddings in some cases
      int add=0;
      switch (bytes.length) {
          case 1: add=6; break;
          case 2: add=4; break;
          case 3: add=3; break;
          case 4: add=1; break;
      }
      // end fix

      StringBuffer base32 = new StringBuffer(((bytes.length+7)*8/5)+add);

      while(i < bytes.length)
      {
          currByte = (bytes[i]>=0) ? bytes[i] : (bytes[i]+256); // unsign

          /* Is the current digit going to span a byte boundary? */
          if (index > 3)
          {
              if ((i+1)<bytes.length)
                  nextByte = (bytes[i+1]>=0) ? bytes[i+1] : (bytes[i+1]+256);
              else
                  nextByte = 0;

              digit = currByte & (0xFF >> index);
              index = (index + 5) % 8;
              digit <<= index;
              digit |= nextByte >> (8 - index);
              i++;
          }
          else
          {
              digit = (currByte >> (8 - (index + 5))) & 0x1F;
              index = (index + 5) % 8;
              if (index == 0)
                  i++;
          }
          base32.append(base32Chars.charAt(digit));
      }

      // begin fix
      // added by jonelo@jonelo.de, Feb 13, 2005
      // according to RFC 3548, the encoding must also contain paddings in some cases
      switch (bytes.length) {
          case 1: base32.append("======"); break;
          case 2: base32.append("===="); break;
          case 3: base32.append("==="); break;
          case 4: base32.append("="); break;
      }
      // end fix

      return base32.toString();
  }

  static public byte[] decode(final String base32)
  {
      int    i, index, lookup, offset, digit;
      byte[] bytes = new byte[base32.length()*5/8];

      for(i = 0, index = 0, offset = 0; i < base32.length(); i++)
      {
          lookup = base32.charAt(i) - '0';

          /* Skip chars outside the lookup table */
          if ( lookup < 0 || lookup >= base32Lookup.length)
              continue;

          digit = base32Lookup[lookup];

          /* If this digit is not in the table, ignore it */
          if (digit == 0xFF)
              continue;

          if (index <= 3)
          {
              index = (index + 5) % 8;
              if (index == 0)
              {
                 bytes[offset] |= digit;
                 offset++;
                 if(offset>=bytes.length) break;
              }
              else
                 bytes[offset] |= digit << (8 - index);
          }
          else
          {
              index = (index + 5) % 8;
              bytes[offset] |= (digit >>> index);
              offset++;

              if(offset>=bytes.length) break;
              bytes[offset] |= digit << (8 - index);
          }
      }
      return bytes;
  }
}
